The invention relates to a hydrostatic piston machine.
In the case of a hydrostatic piston machine in whose housing a cylinder drum is rotatably disposed, the cylinder bores of which can be connected alternately to a control kidney on the intake side and a control kidney on the delivery side, the maximum rotational speed which can be attained is substantially determined by the flow conditions when the pressure medium enters the cylinder bores from the control kidney on the intake side. The inflow of the pressure medium into the cylinder drums on the intake side can be improved by improvements in the fluidic boundary conditions. However, on account of the geometrical conditions, measures of this kind, such as, for example, an enlargement of the through-flow cross section by enlarging the opening in the cylinder drum or the area of the intake kidney, also have limits, as does an improvement of the inflow factor through rounded edges, for example.
It is in addition known from DE 30 18 711 C2 to impose a tangential velocity component on the pressure medium on the intake side, thereby preventing the occurrence of cavitation upon reaching the rotational speed limit. An impeller of a pump is disposed in a connection plate in order to generate a tangential velocity component. The additional pump acts as an auxiliary pump. Its impeller co-operates with a collector. The collector is formed as a channel of a varying flow cross section. The pressure medium which enters the region of the control kidney is composed of two components. On the one hand pressure medium which is directly accelerated by the impeller enters the control opening of the connection plate. On the other hand some of the pressure medium which is drawn in by the impeller is firstly delivered into the collector and returned in a tapering section of the collector to the impeller, where it undergoes further acceleration before it also enters the control kidney.
The described arrangement has the disadvantage of an additional pump which provides the pressure medium drawn in with additional energy being absolutely necessary. Moreover, the arrangement of the impeller in an axial extension of the shaft of the piston machine has the disadvantage of resulting in a significant increase in the construction space of the hydrostatic piston machine. It is in this case impossible to provide a different arrangement, since—on account of the special nature of the impeller the blade ends must be disposed directly in the region of the entrance into the control kidney.
The object of the invention is to provide a hydrostatic piston machine in which the rotational speed limit existing due to the flow conditions on the intake side is raised.